Adolescents who use marijuana and are truant from school are a high-risk population with increased likelihood of substance use disorders, criminal justice involvement, and long-term impairments in vocational, family, and peer domains. This application proposes to test a theory- driven intervention for early adolescent marijuana using, truant youth identified through Rhode Island Truancy and Family Courts. The foundation for this application is a recently completed treatment development study (R34 DA0029871) for marijuana using, truant adolescents (n=67), in which we compared our theory-driven brief intervention, adolescent motivational enhancement therapy (MET) plus the Family Check-Up (FCU), a parent-based MET, to adolescent and parent psychoeducation (PE). There were medium effects favoring the MET+FCU condition on number of marijuana use days in prior 3 months (d = 49) and number of times marijuana was used per day (d= .53). There were also small effects favoring the MET+FCU condition on marijuana craving (d=.36), other drug use (d = .38), number of times more than 5 drinks were consumed per drinking occasion (d=.35), and school absences (d =.30). With respect to mechanisms, medium effect sizes were detected for greater improvement in quality of parent monitoring (d =.58) as well as parent (d = .42) and teen (d = .66) problem- solving discussions in MET + FCU compared to PE. Our pilot results suggest that MET+FCU has the potential to serve as a brief and effective intervention for truant, marijuana using adolescents, but confirmation in a larger, fully powered trial is needed. To speed translation of research findings to practice, this application is proposing to conduct a Type I Hybrid Effectiveness-Implementation trial in which we rigorously test two intervention conditions, while simultaneously gathering data on factors that will impede or facilitate implementation. This application proposes to enroll 200 truant, marijuana using, adolescents in 6th through 10th grades, who are involved in the juvenile justice system through either Truancy Court or Family Court. Adolescents will be randomly assigned to one of the 2 conditions: MET+FCU vs. PE. We will collect data on effectiveness (Specific Aim 1) and putative mediators (Specific Aim 2), as well as data pertinent to implementation (Exploratory Aim). This application is innovative and has the potential to advance the field by: evaluating an integrated model (simultaneously targeting two problems and both parent and teen risk factors), using a brief and highly disseminable approach, examining putative mediators, and testing effectiveness of the interventions under real-world conditions.